A liquid crystal display device using a liquid crystal composition is widely utilized for a display of a watch, a calculator, a word processor or the like. The liquid crystal display devices utilize refractive index anisotropy, dielectric anisotropy or the like of a liquid crystal compound. As an operating mode in the liquid crystal display device, a mode mainly using at least one polarizing plate to display an image is known, such as a phase change (PC), twisted nematic (TN), super twisted nematic (STN), bistable twisted nematic (BTN), electrically controlled birefringence (ECB), optically compensated bend (OCB), in-plane switching (1PS), or vertical alignment (VA) mode. Furthermore, a research has been recently conducted actively into a mode for exhibiting electric birefringence by applying an electric field in an optically isotropic liquid crystal phase (Patent literature Nos. 1 to 16, Non-patent literature Nos. 1 to 3).
Furthermore, a proposal has been made for a wavelength variable filter, a wavefront control device, a liquid crystal lens, an aberration correction device, an aperture control device, an optical head device, or the like utilizing electric birefringence in a blue phase as one of the isotropic liquid crystal phases (Patent literature Nos. 10 to 12).
A classification based on a driving mode in the device includes a passive matrix (PM) and an active matrix (AM). The passive matrix (PM) is further classified into static, multiplex and so forth, and the AM is further classified into a thin film transistor (TFT), a metal insulator metal (MIM) and so forth.
The liquid crystal display devices include a liquid crystal composition having suitable physical properties. In order to improve characteristics of the liquid crystal display device, the liquid crystal composition preferably has suitable physical properties. General physical properties necessary for the liquid crystal compound as a component of the liquid crystal composition are as described below:    (1) being chemically stable and physically stable;    (2) having a high clearing point (clearing point: phase transition temperature between a liquid crystal phase and an isotropic phase);    (3) having a low minimum temperature of the liquid crystal phase (a nematic phase, a cholesteric phase, a smectic phase, an optically isotropic phase such a blue phase, or the like);    (4) having an excellent compatibility with other liquid crystal compounds;    (5) having a dielectric anisotropy of a suitable magnitude; and    (6) having a refractive index anisotropy of a suitable magnitude.
In particular, from a viewpoint of reducing a driving voltage, a liquid crystal compound having both a large dielectric anisotropy and a large refractive index anisotropy is preferred in the optically isotropic liquid crystal phase.
If a liquid crystal compound containing a liquid crystal compound being chemically and physically stable as described in property (1) is used in the liquid crystal display device, a voltage holding ratio can be increased.
According to a liquid crystal composition containing a liquid crystal compound having the high clearing point or the low minimum temperature of the liquid crystal phase as described in properties (2) and (3), a temperature range of the nematic phase or the optically isotropic liquid crystal phase can be extended, and the liquid crystal composition can be used in the form of a display device in a wide temperature range. In order to exhibit characteristics that are difficult to be achieved by a single compound, the liquid crystal compound is generally used in the form of a liquid crystal composition prepared by mixing the compound with many other liquid crystal compounds. Accordingly, the liquid crystal compound to be used in the liquid crystal device preferably has the good compatibility with other liquid crystal compounds as described in property (4). In particular, a liquid crystal display device having a higher display performance in characteristics such as contrast, display capacity and response time, has been recently required. Furthermore, a liquid crystal composition having a low driving voltage is required for a liquid crystal material to be used. Moreover, a liquid crystal compound having the large dielectric anisotropy and refractive index anisotropy is preferably used in order to drive at a low voltage the optical device to be driven in the optically isotropic liquid crystal phase.
The liquid crystal composition in which the compound of the invention is used is described in Patent literature Nos. 15 and 16. However, the liquid crystal composition described in Patent literature Nos. 15 and 16 includes nematic liquid crystals, and no optically isotropic liquid crystals are described therein.
On the other hand, an optically isotropic liquid crystal composition containing a compound represented by general formula (1) according to the invention has a feature of being driven at a low voltage. A composition further containing a compound represented by general formula (2) or (3) in addition to the compound represented by general formula (1) is also driven at a low voltage.